Benchmarking of Separation Methods for Bioethanol (<5 wt %) Recovery

Abstract

Distillation and dehydration account for around 20 to 40% of the total energy consumption for first-generation bioethanol production. Due to the more dilute alcohol concentrations encountered in the second-generation processes, the conventional separation methods are not economically feasible. The main obstacles are the high-energy input demand and low thermodynamic efficiency. In this work, six alternative advanced layouts for alcohol recovery are simulated and benchmarked based on energy consumptions and thermodynamic efficiencies. Among these is the internally heat integrated distillation column, which, despite the research efforts of the last 40 years, is not yet established in the industry. Feed composition has been varied in the range of 0.75–5.0 wt % ethanol. The analysis results show that intensified distillation schemes can improve second law efficiency of about 65 to 80% and reduce energy consumptions by 67% compared to conventional distillation. The most optimal separation technologies investigated requires about 9.8 to 10.4 MJ/kg-EtOH for 0.75 wt % ethanol feed and 1.9–2.0 MJ/kg-EtOH for 5.0 wt % ethanol feed. These are the externally heat-integrated column, the internally heat-integrated column, and a four-effect distillation sequence. The results obtained in this study can allow for more optimal biofuel production, giving rise to potential improved business for sustainable green technology in the future.